All the proceedings set forth in subdivisions (a) to (d), inclusive, shall be exempt from the provisions of Sections 965 and 966 of the Education Code, the Bagley-Keene Open Meeting Act (Article 9 (commencing with Section 11120) of Chapter 1 of Part 1 of Division 3 of Title 2) and the Ralph M. Brown Act (Chapter 9 (commencing with Section 54950) of Part 1 of Division 2 of Title 5), unless the parties mutually agree otherwise:

(a) Any meeting and negotiating discussion between a public school employer and a recognized or certified employee organization.

(b) Any meeting of a mediator with either party or both parties to the meeting and negotiating process.

(c) Any hearing, meeting, or investigation conducted by a factfinder or arbitrator.

(d) Any executive session of the public school employer or between the public school employer and its designated representative for the purpose of discussing its position regarding any matter within the scope of representation and instructing its designated representatives.